Effect of mitogenic stimulation and heat shock on protein syntheses in human T cells

Effects of moderate (42 degrees C, 1 hour) and strong (44 degrees C, 1 hour) heat shocks on resting (TR) and phytohemagglutinin stimulated human T-cells (TP) were studied. Both treatments were shown to cause in the latter considerable fall of the level of protein synthesis, as compared to resting cells. Mitogen-stimulated cells stopped their proliferation irreversibly and part of them (approx: 40%) died after even mild shock (at 42 degrees C). Following heat treatment in both the cell types the synthesis of heat shock 70 and 90 kDa proteins was induced which was much more pronounced in TR. These and earlier results of the authors allow a conclusion that involvement of cells in active proliferation may decrease their resistance to stress, and that this phenomenon coincides with the diminishing in synthesis and accumulation of stress proteins.     

Delay in migration of symbiotic algae in Hydra viridis by inhibitors of microtubule protein polymerization

An English strain of the fresh water symbiotic coelenterate Hydra viridis was experimentally "bleached" of its Chlorella algae and maintained indefinitely by feeding. The algal symbiosis could be re-established by injecting other symbiotic algae into aposymbionts. Although algal uptake and recognition were not affected by microtubule protein polymerization inhibitors, these compounds i.e., podophyllotoxin, beta-peltatin and vinblastine had delaying effects on the migration of the algae through the host digestive cells. Picropodophyllotoxin did not delay migration. The rates, the reversibility and the sensitivity of algal migration to low concentrations of drugs known to bind tubulin suggests the symbionts migrate somehow via labile polymerization of host hydra tubulin into microtubules.     

The Viking mission: Implications for life on Mars

Summary The results of the Viking Biology experiments are best explained by non-biological phenomena: The interaction of the reagents with the materials comprising the regolith. Conditions of water activity, temperature, availability of carbon sources and others in most regions of the planet are too extreme for survival and growth of any known Earth microorganisms. Although the possibility persists that some very unusual form of life is somewhere on that planet the evidence is best interpreted as negative. Even though there is no evidence for current life on Mars, whether or not life ever originated there is not known.     

Tyrosine residues in histones. Kinetics of histones F1 and F2A1 nitration by tetranitromethane]

The kinetics of nitration of tyrosine residues in histones F1 and F2a1 by tetranitromethane has been investigated. At low ionic strength and 30-fold molar excess of nitrating agent the nitration reaction results in fast modification of all tyrosine residues in both histones. At the same time the rates of modification of different tyrosine residues in histone F2a1 are not identical and markedly exceed the rate of N-Ac-OEt-Tyr nitration in a model system. The increase of reaction mixture ionic strength causes an increase of modification rates. The differential UV-absorption spectra of histone F1 obtained by temperature perturbation show an abnormal positive characteristic maximum at 286.8 nm. Analysis of the dependence of nitration rates of tyrosine residues in histones in saline solutions upon the ionic strength and of difference UV-absorption spectra of histones leads to a conclusion that there are specific interactions of definite parts of histone polypeptide chains. These interactions may arise from aggregation of histone molecules.     

Comment of Egami's concept of the evolution of nitrate respiration

Recent results suggest that the presence of common nitrogen salts (sodium nitrite and nitrate) in the irradiation medium can markedly protect filamentous blue green algae from potentially lethal ultraviolet light irradiation. Our results as well as general biological arguments as presented by Egami (above) support and extend Egami's original view that anaerobic respiratory pathways using nitrite and nitrate as terminal electron acceptors evolved prior to oxygen requiring aerobic respiratory pathways.